This invention relates generally to systems and methods for examining eyes. More particularly, the invention relates to systems and methods that employ scanned lines of light for examining eyes.
Fundus imaging is the essential diagnostic procedure in ophthalmology. Instruments of the prior art that are useful for examining the fundus of the eye include direct and indirect ophthalmoscopes, the slit-lamp biomicroscope and the fundus camera. Complementary tools have been developed that broaden diagnostic and therapeutic possibilities, such as the Scanning Laser Ophthalmoscope (SLO). The SLO is a superior tool for rapidly and continuously acquiring high-contrast images of the ocular fundus and its structures, including the distribution of choroidal blood, melanin, and retinal pigments. Because it accommodates a variety of visible and NIR wavelengths, the SLO is especially useful for the study and early diagnosis of diseases such as age-related macular degeneration (AMD) and diabetic retinopathy. These are the leading causes of blindness in the elderly. The SLO is a powerful diagnostic tool for characterizing retinal pathologies, as well as for angiography, tomography, perimetry, and general psychophysics. Confocal SLO imaging is very effective in patients suffering from mild cataract, or from pathologies causing clouding of the vitreous. Another device for examining the fundus of the eye is the instrument described in U.S. Pat. No. 6,267,477, issued on Jul. 31, 2001 to Karpol et al. The Karpol instrument is described as operating on the principle of slit lamp bimicroscopy performed on an eye having a dilated pupil. The Karpol instrument uses a defined angle between a beam going to the retina and a beam returning from the retina, and there is a distance at the area of the pupil between the incident beam and the measured scattered beams. The Karpol instrument uses a two dimensional CCD camera as one of three cameras used to record images.
However, although they have become valuable diagnostic tools in the research community, scanning laser devices have not yet emerged into widespread clinical usage, due in part to their size, cost, and complexity. As a result, they are usually found only at specialized facilities, are used almost exclusively by ophthalmologists, and are often unavailable when needed. In particular, elderly and emergency patients are often unwilling or unable to travel to a specialized clinic for testing. But even the ubiquity of slit-lamps, fundus cameras and indirect ophthalmoscopes does not necessarily allow their use in many circumstances in which they may be indicated, such as emergency care. These devices may not be immediately accessible, and in many circumstances, the primary care physician may not choose to use instruments like Binocular Indirect Ophthalmoscopes (BIO""s) which are more difficult to master, and may be unpleasant for the patient. The fallback device is the direct ophthalmoscope. The availability of hand-held and tele-ophthalmoscopic fundus imaging systems of the standard types are increasing, but their cost remains high, and they continue to have the limitations discussed. A portable, convenient, and less expensive system that provides high quality images of the fundus has been lacking.
The line-scanning laser ophthalmoscope (LSLO) of the invention has a significant confocal advantage in image clarity and contrast, and depth of penetration at the ocular fundus compared with conventional digital fundus photography. The LSLO has features not currently available in commercial SLOs, and is less expensive. The hand-held digital LSLO has proven that high quality, non-mydriatic (e.g., undilated pupil), line-confocal retinal images and stereo pairs can be obtained with a simple, compact design with fewer moving parts and components than current SLO systems. In one embodiment, the system and method involves a monostatic beam geometry, e.g., the light incoming to the thing to be observed, and the light collected in reflection from the thing, pass through the same location in space between the thing and the optical component nearest the thing. As a result of the monostatic beam geometry, the instrument can be operated with a small, undilated pupil. The instrument remains operative even if the pupil is dilated, however.
There are many benefits that accrue if the pupil of an eye is not required to be dilated for the systems and methods of the invention to function correctly. Dilation is generally performed by applying chemicals topically and waiting for the dilation to occur. The waiting period can be some minutes, typically twenty minutes. Absence of a dilation requirement means that an instrument embodying principles of the invention can be used immediately, rather than only after a delay necessitated by the dilation of the pupil. This allows use in settings such as emergency or field use, where other instruments become useful only after the dilation of the pupil is complete. Dilation of the pupil causes the patient to have reduced visual acuity for periods of up to hours, until the effect of the dilation chemicals wears off. Dilation of the pupil can require a patient to use protective eyewear or to avoid light of ordinary intensity. Dilation of the pupil can cause a patient discomfort. The use of an instrument embodying principles of the invention can eliminate all of the above negative features of dilation of the pupil.
The inventive technology provides an affordable clinical instrument that gives the clinician the power and resolution of the SLO, with some operational features of the most familiar ophthalmic diagnostic instruments, in an untethered package that is comparable in size and weight to commercial hand-held digital video cameras.
The LSLO can provide stereo fundus images. A binocular LSLO, with low-cost wearable display technology and more deeply penetrating near-infrared (NIR) light, can provide real time 3-D morphometric information that is usually the domain of slit-lamp biomicroscopes, binocular indirect ophthalmoscopes (BIOs), and stereo fundus photography at shorter wavelengths. NIR operation increases patient comfort and reduces the risk of phototoxicity during extended exams or procedures. By incorporating additional laser wavelengths as additional channels for particular wavelength combinations, color information can be captured and fused with NIR images. The digital LSLO allows the operator to switch views between live-motion and captured still images with the touch of a button. Synchronous modulation of laser illumination with line-by-line image acquisition and variable scans allows stereo images, dual-color images, or fluorescence images to be multiplexed and recorded. The LSLO can be quickly reconfigured for anterior segment imaging, pupil size and light response. The compact and lightweight LSLO offers the potential for use as a hand-held emergency care aid, particularly with blood in the vitreous from eye or head trauma. A portable digital LSLO which performs some of these functions at a cost approaching indirect ophthalmoscopes, while retaining much of the confocal and NIR advantages of the SLO, becomes more clinically versatile and commercially attractive.
In one aspect, the invention relates to a line-scanning laser ophthalmoscope (LSLO). The LSLO comprises a light source providing a substantially point source of light; an optical apparatus and a one-dimensional detector. The optical apparatus comprises an optical component that accepts the light from the laser and provides a line of incoming light, at least one optical component that (i) scans a portion of an eye with the incoming line of light in a direction perpendicular to the line, (ii) confocally receives reflected light from the illuminated portion of the eye, and (iii) provides output light in a line focus configuration; and a turning mirror that redirects a selected one of the incoming light and the reflected light. The one-dimensional detector detects the output light and provides an electrical signal responsive to the output light at each of a plurality of locations along the line of output light.
The light source providing a substantially point source of light comprises a laser. Alternatively, the light source providing a substantially point source of light comprises a super-luminescent diode. The optical component that accepts the light from the light source and provides a line of light comprises one or more lenses. Alternatively, the optical component that accepts the light from the light source and provides a line of light comprises a holographic optical element.
In one embodiment, the LSLO further comprises a signal analysis module that decodes electrical signals from the one-dimensional detector and that generates an array of data representative of reflected light from the illuminated portion of the eye.
In one embodiment, the LSLO further comprises a display module that displays information representative of the array of data generated by the signal analysis module. The one-dimensional detector is a linear CCD array or a linear CMOS array in some embodiments. In a preferred embodiment, the laser is an infrared laser. In a more preferred embodiment, the infrared laser operates at a wavelength in the range of 700 nm to 950 nm. In a still more preferred embodiment, the infrared laser operates at a wavelength of substantially 830 nm.
In some embodiments, the optical apparatus of he LSLO further comprises a scanning mirror that provides a scanned line of light having a scan direction perpendicular to the line of light, one or more lenses that focus the scanned line of light on a portion of an eye, one or more lenses that confocally receive reflected light from the illuminated portion of the eye and provide a line of reflected light, a scanning mirror that redirects the line of reflected light, a pupil stop that prevents unwanted light from proceeding through the optical apparatus, and an objective lens that focuses the redirected line of reflected light onto the one-dimensional detector.
In a preferred embodiment, the scanning mirror that intercepts the redirected line of light and provides a scanned line of light and the scanning mirror that redirects the line of reflected light are the same scanning mirror. In a preferred embodiment, the one or more lenses that focus the scanned line of light on a portion of an eye and the one or more lenses that confocally receive reflected light from the illuminated portion of the eye are the same one or more lenses. In some embodiments, the pupil stop prevents non-confocally received light from proceeding through the optical apparatus.
In still another aspect the invention features a line-scanning ophthalmoscope. The line-scanning ophthalmoscope comprises a light source providing a substantially point source of light, an optical apparatus and a one-dimensional detector. The optical apparatus (i) receives light from the light source, (ii) scans a portion of an eye with the line of light in a direction perpendicular to the line, (iii) confocally receives reflected light from the illuminated portion of the eye, and (iv) provides output light in a line focus configuration. The one-dimensional detector detects the output light and provides an electrical signal responsive to the output light at each of a plurality of locations along the line of output light.
In yet a further aspect, the invention relates to a line-scanning laser ophthalmoscope (LSLO). The LSLO comprises a light source providing a substantially point source of light; an optical apparatus and a one-dimensional detector. The optical apparatus comprises an optical component that accepts the light from the laser and provides a line of incoming light, at least one optical component that (i) scans a portion of an eye having an undilated pupil with the incoming line of light in a direction perpendicular to the line, (ii) confocally receives reflected light from the illuminated portion of the eye, and (iii) provides output light in a line focus configuration, and a turning mirror that redirects a selected one of the incoming light and the reflected light. The one-dimensional detector detects the output light and provides an electrical signal responsive to the output light at each of a plurality of locations along the line of output light.
In a further aspect, the invention relates to a line-scanning laser ophthalmoscope (LSLO). The LSLO comprises a light source providing a substantially point source of light; an optical apparatus and a one-dimensional detector. The optical apparatus comprises an optical component that accepts the light from the laser and provides a line of incoming light, at least one optical component that (i) scans a portion of an eye with the incoming line of light in a direction perpendicular to the line, (ii) confocally receives reflected light from the illuminated portion of the eye, the incoming line of light and the reflected light having monostatic beam geometry, and (iii) provides output light in a line focus configuration, and a turning mirror that redirects a selected one of the incoming light and the reflected light. The one-dimensional detector detects the output light and provides an electrical signal responsive to the output light at each of a plurality of locations along the line of output light.
In a further aspect the invention relates to a method of making a optical measurement of an object. The method includes the steps of providing an incoming line of light, scanning a portion of an object with the incoming line of light in a direction perpendicular to the line, confocally receiving reflected light from the illuminated portion of the object, providing output light in a line focus configuration from the received reflected light, separating the incoming light and the output light, detecting the output light, and providing an electrical signal responsive to the output light at each of a plurality of locations along the line of output light. In one embodiment, the object is an eye. In one embodiment, the method further comprises the steps of decoding the electrical signal, and generating an array of data representative of reflected light from the illuminated portion of the object.
In still a further aspect, the invention includes a method of making an ophthalmoscopic measurement. The method includes the steps of providing an incoming line of light, scanning a portion of an eye having an undilated pupil with the incoming line of light in a direction perpendicular to the line, confocally receiving reflected light from the illuminated portion of the eye, providing output light in a line focus configuration from the received reflected light, separating the incoming light and the output light, detecting the output light, and providing an electrical signal responsive to the output light at each of a plurality of locations along the line of output light.
In yet an additional aspect, the invention relates to a method of making an ophthalmoscopic measurement. The method includes the steps of providing an incoming line of light, scanning a portion of an eye with the incoming line of light in a direction perpendicular to the line, and confocally receiving reflected light from the illuminated portion of the eye, using a monostatic beam geometry for the incoming line of light and the reflected light. The method also includes the steps of providing output light in a line focus configuration from the received reflected light, separating the incoming light and the output light, detecting the output light, and providing an electrical signal responsive to the output light at each of a plurality of locations along the line of output light.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.